The invention relates to an apparatus for creating a knitted fabric with interspacing, in particular a knitted fabric with a spacing of more than 14 mm between surfaces. The invention furthermore relates to a method for producing such a knitted fabric with interspacing.
Textile materials with spaced apart surfaces are frequently used for industrial textiles and specific functional clothing, wherein both textile surfaces are connected by pile threads. Known are only knitted fabrics with interspacing ranging from 3 mm to 14 mm between surfaces, as well as weft and woven fabrics up to a height of 60 mm and above. The height represents the distance between the two textile surfaces, which are connected to each other by a pile thread, wherein a monofilament thread is frequently used as pile thread. Alternative to weft and woven fabrics with interspacing, a knitted fabric can be produced on a circular knitting machine with knitting cylinder and dial. For example, the one knitted fabric surface in the shape of a tube is produced with the needles of the dial and the other, also tubular knitted fabric surface is produced with the needles of the knitting cylinder. Both knitted surfaces are connected by the back and forth moving monofilament thread. The distance between the knitted surfaces depends on the distance between the knitting cylinder and the dial.
The spacing between the dial and the knitting cylinder, however, cannot be optionally large to satisfy the desire to have larger distances between knitted surfaces because the distance between dial and knitting cylinder must be bridged by the needles in the extended state. A longer distance inside the needle cam is required for a further extension of the needles, meaning longer cams have to be used. If longer cams are used, the productivity of the machine is reduced by the same degree because longer cams mean that fewer cam curves are possible over the circumference of a circular knitting machine. The system number at the diameter for the circular knitting machine is thus reduced, which results in fewer rows of loops per machine rotation.
A circular knitting machine for producing knitted fabrics with interspacing is known from document DE-OS 103 20 533. For the loop forming, compound needles are used for at least one embodiment of this machine. Distances between the knitted surfaces of up to 14 mm can be realized with this machine.
However, compound needles require cams which have a cam curve not only for the needle, but also for the closing element. Cams of this type are more involved than cams for latch needles. In addition, the use has limits if the distances between the knitted surfaces must exceed 14 mm because longer cams are needed in that case as a result of the excessive extension. In that case the above statement relating to the productivity of the knitting machine applies. If longer cams are used, the productivity of the machine is reduced by the same degree because longer cams mean that fewer cam curves are possible over the circumference of a circular knitting machine.
When producing knitted fabrics with interspacing using latch needles, the distance between both textile surfaces among other things depends on the length of the latch and/or the hinge for the latch needles. The connecting thread for both textile surfaces must be inserted into the dial needle as well as the cylinder needle during the tie up in the tuck position. In the process, the two needles can be extended maximally far enough, so that the thread positioned in the hook, which is used for the loop forming, remains on the needle latch that is still in the rear or retracted position and does not slide across the inside edge of the needle latch and onto the needle shank. Thus, the distance between both textile surfaces when using latch needles is limited to their maximum latch motion. This is true in particular for a knitting machine as disclosed to document U.S. Pat. No. 6,122,690, for which two needle cylinders are arranged coaxially opposite each other. Both needle cylinders are provided with latch needles. This document discloses the transfer of the loops from a needle on a first knitting cylinder to a needle on a second knitting cylinder. When using the knitting cylinder arrangement according to document U.S. Pat. No. 6,122,690 for producing knitted fabrics with interspacing, the distance between two knitted textiles is limited by two times the latch motion less one time the hook size, since the pile thread is inserted into both hooks of the knitting machine needles. Knitted fabrics with an interspacing of approximately 10 mm between the knitted surfaces can thus be produced.